The present invention relates to a semiconductor memory device and a method of manufacturing the semiconductor memory device, and more specifically to a MOS type semiconductor memory device such as a DRAM (Dynamic Random Access Memory) or the like, which is capable of being brought into high density and a method of manufacturing the semiconductor memory device.
Many endeavors have heretofore been carried out to improve the density of integration of a semiconductor memory device as has already been known. In a DRAM cell which has been proposed in Japanese Patent Application No. 2-115642, for example, three-dimensional capacitors laid over memory cell regions, whose plane areas and circumferential lengths have been reduced to about 3/8 and about 2/3 respectively, have been formed.
In the prior art, however, the total area of the capacitors is about three to four times the area of each memory cell and capacitors each having a surface area greater than such an area are not yet obtained. Therefore, the area of a capacitor is greatly reduced each time the generation is changed from one to another in the case of a DRAM in which the area of each memory cell is reduced to about 1/3 for each generation. It has also been hard to stably activate the DRAM without being disturbed by noise such as .alpha.-rays from other region.
There has therefore been a strong demand for a semiconductor memory device capable of providing a less reduction in the total area of the capacitors and keeping the total area of capacitors great even when the area of each of memory cells is reduced.